The present disclosure relates to systems and methods for treating subterranean formations.
Production of oil and gas from subterranean formations may be hindered by formation damage. Most damage occurs due to introduction of fluids and high pump rates that cause swelling and/or mechanical damage in the formation. Formations are prone to water-sensitivity, which can cause damage through swelling, softening, dissolving, forming precipitates, polymer aggregates, sloughing and/or generating migrating fines. The reaction of water with formation minerals produces damage, including weakening, swelling, dispersion, and flocculation, which could lead to significant loss of fracture conductivity in both primary and secondary fractures. Proppant placed in the formation also may crack, break, or degrade when subjected to closure stresses and fluids in the formation, which may cause similar losses of fracture conductivity. All of these issues can potentially decrease production or induce wellbore damage.
In some formations, clays or fines may already be present or fines may be generated during formation treating activity. In some instances, the formation is stable causing no obstruction to the flow of hydrocarbons through the subterranean formation. However, when the formation is not stable, the minerals can swell and/or fines can migrate through the formation until they become lodged in pore throats, thereby decreasing the permeability of the formation. Various treatment products and methods may be available for treating these issues, although different treatments may vary in efficacy in a given formation depending on the cause and/or mechanism of damage in that formation as well as its fluid sensitivity. Laboratory testing methods have been developed to quantify and ascertain the extent and causes of fluid sensitivity and damage for a formation, including X-ray diffraction (XRD), swelling stability tests (SST), mechanical stabilization tests (MST), cation exchange capacity (CEC), and coreflooding. However, each of these test methods may have certain limitations. For example, XRD may be useful for identifying the crystalline materials within the formation, but it cannot be used to predict all impacts from fluid. SST results may be useful for diagnosing clay-induced swelling damage and determining treatments that protect the formation, but SST is only sensitive to swelling and is unresponsive to other damage mechanisms. CEC may correlate well with various mechanical properties that relate to a diverse set of formation damage mechanisms; however, the method is unable to diagnose the different damage mechanisms and cannot be used to determine the effectiveness of treatments. Coreflood testing is not always possible for certain types of shales having very low permeability (e.g., nanodarcy shales).
While embodiments of this disclosure have been depicted, such embodiments do not imply a limitation on the disclosure, and no such limitation should be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.